Subject: RE: New Internet Draft on automatic (end-user) tunneling for SSM

From: "Dave Thaler" <[email-masked]>
Date: Mon, 5 Mar 2001 16:31:21 -0800

Ross writes:
> In contrast, I worry about how easy it would be to deploy 
> schemes that 
> require a separate 'tunnel endpoint location' mechanism.  In 
> particular, 
> the "AMT" draft (Thaler at al) proposes using "anycast" to 
> find tunnel 
> endpoints.  However, do we expect anycast to be widely 
> available - even by 
> users of J. Random Non-Multicast-Connected ISPs?  Aren't some 
> providers 
> likely to filter out anycast routes (because of the length of 
> their 'prefix')?

If you read the draft, you'll see that the answer to your
last question is "yes which is why it uses an anycast
prefix not just a /32 anycast address".  As a result,
the answer to your next-to-last question is "yes,
this type of anycast is widely available now". 

This same discussion for IPv6 connectivity happened in the 
NGtrans WG regarding 6to4 a while ago, with the consensus 
being the same mechanism used in the AMT draft.

Chewing up lots of address space to get around prefix filters
is certainly not a general solution to anycast.  However,
for a few special-cases (such as relieving different address
space problems, for example), it is seen as acceptable.

-Dave